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Clone SD card for new system <- Re: change hostname & static IP & ???

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On 04/11/2016 09:31 PM, David Wright wrote:
> On Mon 11 Apr 2016 at 19:02:45 (-0400), ken wrote:
>> This is on Wheezy for a Raspberry Pi.
>>
>> Using dd, I copied the SD card for one (nicely working and
>> configured) system onto another SD card.  I want to use this second
>> card for another system, so need to change the hostname and (static)
>> IP address.  Yesterday I grepped the whole system for one and then
>> the other and where I found either, I made appropriate changes
>> (i.e., previous hostname to new hostname, previous IP address to new
>> IP address).  I also zeroed out all text-based files in /var/log/
>> (e.g., >messages), just to start the new system with clean logs.
>>
>> Both the previous (still running) system and the new one (not yet
>> running) are to be on the same LAN, so I'm pretty certain that no
>> other networking configuration-- like broadcast or netmask-- needs
>> to be touched (how could it need any?).
>>
>> Neither of these systems has any public-facing services currently running.
>>
>> My concerns are these:
>>
>> Only files which grep could find were amended. (Note that grep was
>> run on the card when it was mounted on another system, not when the
>> system on that card was booted and running.)  Is there a file of
>> some kind, perhaps, which encodes either the hostname and/or IP
>> address in such a way that would hide it/them from grep?
> If you regenerate ssh keys, your .ssh/known_hosts files will have
> hostnames and IP numbers you might want to remove. They're encrypted.
> You could blank them like the log files.
>
> The key pairs themselves only have visible hostnames in the public
> part's file.

Ah, yes!  Thanks.  Some brain cells knew that, but were sleeping.  But 
actually I want to keep that ~/.ssh/known_hosts so I can ssh from this 
new RPi to the other machines on my LAN without having to reconfigure 
all that ssh stuff... one of the several time-saving reasons I'm 
(quasi-)duplicating the SD card.

But you bring up a very good point: I don't want the new system to have 
the same /etc/ssh/ssh_host_*key* files that the previous system has.  
Though it might work okay, still I think the sshd host keys are meant to 
be unique across all LAN'd systems (ideally unique in the universe).  So 
I think I need to do "rm etc/ssh/ssh_host_*key*" so that sshd knows 
they're gone; in the past IIRC these host keys were automatically 
created, probably done in the sshd script under init.d;  I hope that 
it's the same under the new-fangled systemd code.


>> Since people are supposed to be able (I think, never done) to take
>> an SD out of one RPi and put and boot it in another RPi (with the
>> same hardware), I didn't make any attempt to find and change any
>> hardware designations, like the MAC address of the NIC.  Is that
>> okay?
>>
>> Your router may know IP#/MAC combinations for dhcp.

I'm not using dhcpd on the router, so that won't affect me. But for 
those who do, if you can do "arp -a" on your router, that will show 
which MAC addresses are cached; "arp -d address" will delete that 
address's entry in the arp table, allowing/obligating the system to 
generate a/the new entry.


>>
>> Also IPv6 link-local addresses are generated from the MAC address
>> (in case you've told them to any of your other machines).

Again, not using that, but others may, so find the info useful.  Thanks.


>>
>> Cheers,
>> David.
>>

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Thread

change hostname & static IP & ??? ken <gebser@mousecar.com> - 2016-04-12 01:10 +0200
  Re: change hostname & static IP & ??? David Wright <deblis@lionunicorn.co.uk> - 2016-04-12 03:40 +0200
    Re: change hostname & static IP & ??? <tomas@tuxteam.de> - 2016-04-12 09:30 +0200
      Re: change hostname & static IP & ??? ken <gebser@mousecar.com> - 2016-04-12 23:30 +0200
        Re: change hostname & static IP & ??? David Wright <deblis@lionunicorn.co.uk> - 2016-04-13 02:40 +0200
        Re: change hostname & static IP & ??? <tomas@tuxteam.de> - 2016-04-13 09:50 +0200
    Clone SD card for new system <- Re: change hostname & static IP & ??? ken <gebser@mousecar.com> - 2016-04-12 16:30 +0200
      Re: Clone SD card for new system <- Re: change hostname & static IP  & ??? David Wright <deblis@lionunicorn.co.uk> - 2016-04-13 02:10 +0200
  Re: [Raspbian-devel] change hostname & static IP & ??? Stian Skjelstad <stian@barnfind.no> - 2016-04-12 09:40 +0200

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